A governing principle in medical ethics is respect for patient autonomy. This principle is commonly drawn upon in order to argue for the permissibility of assisted dying. In this paper I explore the proper role that respect for patient autonomy should play in this context. I argue that the role of autonomy is not to identify a patient’s best interests, but instead to act as a side-constraint on action. The surprising conclusion of the paper is that whether or not it is in the best interests for the patient to die is a morally objective matter. This allows for the possibility that it can be in the best interests of the patient to die even if she autonomously considers it to be in her best interest to continue living. I argue that concerns about ‘mandatory’ euthanasia can be met when patient autonomy is respected as a side-constraint on action. Ultimately, this means that assisted dying is permissible, not because the autonomous patient views her suffering to be unbearable, but because it is in her objective best interests and she permitted it via her consent.